Sir Alex Ferguson has admitted a growing concern at Owen Hargreaves' continued absence through injury.

The Manchester United boss confirmed Hargreaves has returned to Munich for further treatment on the hamstring injury he suffered against Wolves in November that has consigned him to another lengthy spell on the sidelines.

Hargreaves was making his first start for over two years following operations on both knees to cure a serious tendinitis problem and Ferguson has previously admitted he has no idea when the 29-year-old will return.

As his contract is due to expire at the end of the season, Hargreaves' United future is uncertain at best.

And Ferguson admitted to worries about whether Hargreaves can even return to the field in any capacity, let alone the level that saw him selected as England's best player at the 2006 World Cup.

"We are all concerned," said the United chief.

"He has not played for over two years so we would have to be super-optimistic to think everything in the garden was rosy about him making comebacks.

"What we are trying to do is help the lad. That in itself is our biggest challenge. We want to help the lad try to get back to a level where he can still play football."

Ferguson insists Hargreaves was ready to make his comeback when he was thrown into the fray earlier this season, even though he had no warm-up games as build-up.

The midfielder signalled there was a problem within a couple of minutes of kick-off, and though he did try to battle through the pain, he found it was impossible.

"This hamstring injury is a real kick in the teeth," said Ferguson.

"He was doing so well in training before the Wolves game. He was absolutely superb.

"There were no qualms whatsoever about putting him in, even though he had only trained for nine days.

"We were confident enough to play him but unfortunately it has proved to be a disappointment for us.

"If he had realised early enough and come off before he had done any more damage, it could have been three to four weeks. But is a complete tear."

Hargreaves has not offered his own feelings on the matter, although Ferguson acted with incredulity when asked how the former Bayern Munich star would be affected.

There must be a possibility that the player will ultimately decide to quit the game.